The long term objective of the proposed research is to gain a strong understanding of the complex and conflicting role that phenolic-based compounds play in vivo. They can be pro-oxidants and antioxidants, carcinogenic and chemotherapeutic; activities that defy comprehension at this time. Patterns of behavior of simple and complex phenols have not been systematically addressed for a very important class of compounds whose reactive functional group is ubiquitous in nature and present in a large number of foods, drugs, and nutraceuticals that are consumed by the general public. Their mechanisms of action at the molecular level have also not merited the attention that they deserve. Specific Aim 1 of this proposal will focus on the ability of copper-mediated phenols to evoke oxidative DNA damage, specifically the formation of abasic sites in calf thymus DNA. The caspase-mediated apoptotic inducing activities of simple monosubstituted phenols and sterically hindered phenols will also be examined via a fluorometric assay using a tetrapeptide-rhodamine substrate, to determine what intermolecular forces are at play in the cell-based assays. Specific Aim 3 will determine the direct effects of phenols on caspases 1, 3, 8, and 9 and on mitochondrial membrane potentials in vitro, in order to delineate which apoptotic pathway (intrinsic or extrinsic) is compromised in phenol exposed cells. The effects of antioxidants and a caspase inhibitor on phenol-induced apoptosis will also be assessed. Specific Aim 4 will attempt to ascertain the degree of DNA repair after phenol insult by a measure of DNA recombination events in yeast. In Specific Aim 5, the Quantitative Structure-Activity Relationship (QSAR) paradigm will be utilized to unravel the many physicochemical variables that control these reactivities and biological activities of phenols. Phenols constitute an important class of molecules whose reactive behavior is not well understood. The phenolic moiety behaves in a bewildering manner depending on its overall structural environment, concentration and nature of cells and tissues. The toxicity associated with phenols is generally attributed to their oxidative activation. Their complexity in behavior, prevalence in nature, and extensive usage warrants a more systematic and current assessment of their ability to induce both DNA damage at the molecular level, apoptosis at the cellular level, and carcinogenesis in some animal species. It is envisioned that the combined experimental-computational approach to phenol toxicity will provide guidance for the inclusion or exclusion of the OH group from new drug entities. [unreadable] [unreadable]